1. Field of the Invention
The present invention relates in general to a shock absorbing structure for a motor vehicle and a shock absorbing assembly including the same. More particularly, the invention relates to an improved shock absorbing structure disposed in an installation space defined by and between a vehicle component and a vehicle body, and a shock absorbing assembly wherein the shock absorbing structure is advantageously installed or mounted on the vehicle component.
2. Discussion of Related Art
Conventionally, a shock absorbing structure for absorbing impact energy is provided or disposed between various components of a motor vehicle or other motor vehicle and a body of the vehicle. The shock absorbing structure disposed as described above is arranged to be deformed for absorbing a shock or impact generated by contact of a passenger or driver of a vehicle (hereinafter referred to as “vehicle passenger”) or a pedestrian with the vehicle component in the event of a collision of the vehicle from an accident, thereby assuring improved safety of the vehicle passenger or the pedestrian.
There are known various types of shock absorbing structure having various shock absorbing characteristics. Among various types of shock absorbing structure, a suitable one is selected so as to satisfy the conditions for installing the shock absorbing structure between the vehicle component and the vehicle body, the shock absorbing characteristics required by the vehicle component, etc.
There is known a shock absorbing structure disposed in a considerably narrow or small installation space having a size of not greater than about 20 mm, such as a space defined by and between a roof reinforcement located over a front pillar and a ceiling interior member of a vehicle, which space is considerably narrower or smaller than the other space defined by and between the vehicle body and the vehicle components other than the ceiling interior member. One example of such a shock absorbing structure includes a planar rectangular top wall portion to which the shock is applied and two planar leg walls formed integrally with the top wall portion such that the two leg walls respectively extend from opposite two side edges of the top wall portion so as to be opposed to each other, toward one of opposite sides of the top wall portion as seen in a direction of thickness thereof. The known shock absorbing structure is formed of a thin steel plate and has a generally U-shape in cross section.
The above-described shock absorbing structure formed of the steel plate and having the U-shaped cross sectional shape is generally disposed in a space between the roof reinforcement and the ceiling interior member of the vehicle, such that the two leg walls extend in a direction in which the roof reinforcement and the ceiling interior member are opposed to each other. In other words, the shock absorbing structure described above is disposed in the space such that the two leg walls extend in a direction in which the shock is applied from an external to the ceiling interior member. With the shock absorbing structure being thus disposed in the space, when the shock is applied to the shock absorbing structure by contact of the vehicle passenger with the ceiling interior member in the event of a collision from an accident, for instance, the distal portions of the two leg walls slide on the ceiling interior member or the roof reinforcement so as to be displaced away from each other. Thus, the two leg walls are deformed so as to be displaced away from each other such that a rate of increase in a distance between the two leg walls in a direction in which the two leg walls are opposed to each other gradually increases with an increase in a distance in a direction which is perpendicular to that direction and which is away from the top wall portion toward the distal portions of the leg walls, for thereby absorbing the impact energy. (The deformation described above is referred to as “opening deformation”.)
In the meantime, in a shock absorbing structure having cylindrical members made of resin, a shock absorbing structure in which a plurality of resin-made ribs are arranged in lattice on a base plate, or a shock absorbing structure formed of resin foamed body, for instance, an entirety or a portion of each shock absorbing structure is subjected to buckling deformation or collapsing deformation for absorbing the impact energy. In contrast, in the above-described shock absorbing structure formed of the steel plate and having the U-shape in cross section, it is less likely that deformed portions are superposed on each other, so that the height of the structure after deformation can be made sufficiently small. Accordingly, even if the height of the shock absorbing structure before deformation is made small so as to correspond to a size of a small or narrow installation space in which the structure is to be disposed, an effective stroke index of the structure, i.e., a ratio of an amount of deformation of the shock absorbing structure by application of the shock thereto to the height of the shock absorbing structure before deformation, can be made sufficiently large, so that the shock absorbing structure exhibits excellent shock absorbing capability with high reliability.
However, the above-described shock absorbing structure formed of the steel plate and having the U-shape in cross section is generally attached to the vehicle body at local points thereof by spot welding, screw-fastening, etc. Accordingly, the shock absorbing structure when disposed in the space between the vehicle component and the vehicle body inevitably suffers from a variation in its shock absorbing characteristics at different portions thereof depending upon whether the portions are fixed to the vehicle body or not.
In the meantime, there is conventionally known a shock absorbing structure, as disclosed in JP-A-2000-211454, which includes resin main bodies each having a generally U-shape in cross section and including a top wall and two leg walls which are formed integrally with each other by using a synthetic resin material. In such a shock absorbing structure formed of resin, an entirety of one of opposite major surfaces of the top wall is bonded to the vehicle component or the vehicle body, for instance. Alternatively, where the vehicle component is made of a synthetic resin material, the entirety of one of opposite major surfaces of the top wall and a portion of the vehicle component corresponding to the top wall are welded together, so that the resin shock absorbing structure is attached to the vehicle component or the vehicle body at local areas thereof by a so-called welding operation. Accordingly, the shock absorbing structure bonded to the vehicle component or the vehicle body at local areas thereof does not suffer from the above-described problem of variation of the shock absorbing characteristics experienced in a case where the conventional shock absorbing structure formed of the steel plate and having the U-shape in cross section is fixed to the vehicle body at local points thereof.
The shock absorbing structure which includes the resin main bodies having the U-shape in cross section and which is disclosed in the above-described Publication, however, is adapted to absorb the impact energy such that the leg walls are subjected to buckling deformation upon application of the shock to the structure from the external. Accordingly, the disclosed shock absorbing structure does not have the effective stroke index as large as that in the above-described shock absorbing structure formed of the steel plate and having the U-shape in cross section. The shock absorbing structure disclosed in the Publication exhibits a sufficiently high degree of shock absorbing capability if it is disposed in an installation space having a certain degree of size. The disclosed shock absorbing structure, however, inevitably suffers from insufficient shock absorbing capability if it is disposed, in its known structure without any modification, in a considerably small or narrow installation space between the vehicle component and the vehicle body, in place of the above-described shock absorbing structure formed of the steel plate and having the U-shape in cross section.
It might be considered possible, for instance, that the configuration of the resin main body is modified such that the two leg walls are not subjected to the buckling deformation, but subjected to the above-described opening deformation upon application of the shock to the resin main body, in other words, the two leg walls are deformed such that a rate of increase in a distance between the two leg walls as measured in a direction in which they are opposed to each other gradually increases with an increase in a distance as measured in a direction which is perpendicular to that direction and which is away from the top wall toward distal portions of the leg walls, for the purpose of improving the shock absorbing capability exhibited when the resin shock absorbing structure having the resin main bodies is disposed in the considerably narrow or small space.
Even if the leg walls are arranged to be subjected to the opening deformation described above by optimizing the configuration of the resin main body, the resin shock absorbing structure may undergo stress concentration at corners formed by the top wall and the leg walls when the leg walls are subjected to the opening deformation, so that there may be generated cracking or fracture at the corners, causing a risk that the shock absorbing structure is not capable of absorbing a desired amount of impact energy.